Solution 1H NMR characterization of substrate-free C. diphtheriae heme oxygenase: Pertinence for determining magnetic axes in paramagnetic substrate complexes

Zhenming Du, Masaki Unno, Toshitaka Matsui, Masao Ikeda-Saito, Gerd N. La Mar

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)

Abstract

Proton 2D NMR was used to confirm in solution a highly conserved portion of the molecular structure upon substrate loss for the heme oxygenase from the pathogenic bacterium Corynebacterium diphtheriae, HmuO. The chemical shifts for the conserved portion of the structure are assessed as references for the dipolar shifts needed to determine the orientation of the paramagnetic susceptibility tensor, χ, in paramagnetic substrate complexes of HmuO. It is shown that the chemical shifts for the structurally conserved portion of substrate-free HmuO serve as excellent references for residues with only small to moderate sized dipolar shifts in the cyanide-inhibited substrate complex of HmuO, yielding an orientation of χ that is essentially the same as conventionally obtained from large dipolar shifts based on empirical estimates of the diamagnetic reference. The implications of these diamagnetic chemical shifts for characterizing the hydrogen bonding in the physiologically relevant, resting-state, high-spin aquo complex are discussed. The pattern of labile proton exchange in the distal H-bond network of substrate-free HmuO allowed comparison of changes in dynamic stability of tertiary contacts in the substrate-free and substrate-bound HmuO and with the same complexes of human heme oxygenase.

Original languageEnglish
Pages (from-to)1063-1070
Number of pages8
JournalJournal of Inorganic Biochemistry
Volume104
Issue number10
DOIs
Publication statusPublished - 2010 Oct

Keywords

  • Aromatic cluster
  • Corynebacterium diphtheriae
  • Heme oxygenase
  • Magnetic axes
  • Molecular structure

ASJC Scopus subject areas

  • Biochemistry
  • Inorganic Chemistry

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